In recent years, ITU-R (International Telecommunication Union-Radiocommunication sector) has enrolled the IMT (International Mobile Telecommunication)-Advanced system. In 3GPP (3rd Generation Partnership Project), LTE-Advanced (hereinafter, referred to as LTE-A) capable of improving the system performance while maintaining compatibility with Rel.8 LTE (Release 8 Long Term Evolution) has been standardized. It is not easy for the macro cell system which is the base of the cellular system and in which cells around the base station cover the service areas to satisfy capacity and coverage required in the future.
The heterogeneous network (hereinafter, also referred to as HetNet) in which a low-power local node is arranged in the cells of the macro cell system has been examined for LTE-A (see Non Patent Literature 1). FIG. 22 is a diagram illustrating an example of a HetNet scenario. As shown in FIG. 22, five cases have been examined as the HetNet scenario. One of the five cases is the mixture of a macro cell and a femtocell (see Case 5.1). FIG. 23 shows an example of the HetNet. A femtocell (Home eNB: HeNB) is disposed in the vicinity of the macro cell (evolved Node B: eNB). As shown in FIG. 23, a terminal (user equipment connected to Macro eNB: MUE in FIG. 23) in area 1 is connected to the macro cell (Macro eNB) and a terminal (user equipment connected to Home eNB: HUE in FIG. 23) in area 2 is connected to the femtocell (in FIG. 23, HeNB). Area 1 covered by the macro cell (Macro eNB) is larger than area 2 covered by the femtocell.
In LTE-A, a carrier aggregation simultaneously using a plurality of component carriers (hereinafter, also referred to as CCs) has been examined. When a plurality of CCs are adjacent to each other, an extension carrier or a carrier segment for effectively using the frequency band between the CCs has been examined.
FIG. 24 is a schematic diagram illustrating the extension carrier. In FIG. 24, the vertical axis indicates time and the horizontal axis indicates a frequency. In FIG. 24, for distinguishing a plurality of CCs, the carrier components are represented by CC1 and CC2, and the extension carrier or the carrier segment is simply represented as an extension carrier part. In FIG. 24, an RB (Resource Block) is a resource unit including 12 sub-carriers of one sub-frame in LTE or LTE-A. Each CC shown in FIG. 24 is one sub-frame unit.
When each CC is used, a guard band (GB) is provided in order to reduce interference with an adjacent system band. However, when a plurality of adjacent carrier components CC1 and CC2 are used in the same LTE-A, it is possible to reduce the guard band GB between the carrier components CC1 and CC2. Therefore, as shown in FIG. 24, in order to effectively use the frequency band between the carrier components CC1 and CC2, the extension carrier or the carrier segment is added to the original band (Backward Compatible Part) defined in LTE. In FIG. 24, the backward compatible part is 100 RBs and the extension carrier part is 10 RBs for each CC.
The extension carrier and the carrier segment are similar to each other in that RB (Resource Block) is physically added to the original CC (CC defined in LTE; hereinafter, also referred to as the backward compatible part). However, the extension carrier differs from the carrier segment in that it is treated as a CC different from the original CC and the carrier segment is treated as resources associated with the original CC (see Non Patent Literature 2).